Beginner PHP Tutorial - 56 - Creating a Find and Replace Application Part 3 Video Lecture | PHP for Absolute Beginners: From Novice to PHP Master - Web Development

the cat sat on the map we want to search
for cat
so in fact let's put cat there as well
so we want to search for cat there are
two instances of the word cat inside
this string here so what we need to do
is we need to start an offset of zero
let's pull all this down so it doesn't
distract us we're starting the offset of
zero so it's going to start from before
the T this is position zero this is why
we remember we start at zero so we're
going to go zero one two three four is
where it is where the see start so one
two three four that's where it starts
now our position is our offset is now
equal to floor oh no sorry this
substring equals four and our offset
equals zero still it's probably a better
way to represent it so we've set zero
one two three four and we've got to this
C here now our offset the next while
round the loop wants to be here so we
need to add three characters to it
however how do we know how many
characters to add to it or we need to
obtain the length of the search term in
order to add to the offset so what we
need to do is we need to first of all
set the offset to the the value let me
think hold on so substring for my
substring is equal to four we need to
set the offset equal to substring add
the amount of characters in here so the
substring will now become 4 and 3 which
is 7 so now the offset 7 the next wire
around the loop we're going to go 1 2 3
4 5 6 7 we've missed out this because
we've already found this we don't need
to process this now it's going to search
from here and it's going to find another
instance of it here and then it will do
exactly the same thing as I've just
explained
so if you don't understand this rewind
the video and listen to to what I've
said again and try and understand how
these variables are being set each time
remember we can use the string Len
function with this cat to obtain the
length of the string so that's not a
problem so let's put this into action
put my words into action and let's pull
it up and so we're in the loop let's say
this returns as four like we did before
so remember it was four characters now
we don't need to think about this yet we
just need to do the code and then we can
test to see if it works
so the offset is now going to be equal
to STR pause add and we need to add the
string length of the search text so
let's come over here and say search
length equals STR lead this is going to
return this the length of the string in
a integer so search now what we do is
just add that on okay so now what will
happen is the next right the next while
round this loop the offset will
dynamically change because we've used a
variable here we've changed the variable
here when we started at zero each time
around the loop this is going to be
dynamic and change so let's echo this
out each time put a line break on the
end so we can test what we're doing so
the cat sat on the mat or the cat sat on
the cat we're going to search for cat
we're replacing with at the moment this
doesn't matter because we haven't taken
this into account in our program so we
click find a replace a will return with
7 and 22 now this is disappeared but
let's just retype it now let's to double
check that everything's right so 1 2 3 4
5 6 7 remember we're starting now from
there we've already we've already got
the substrate in fact let's echo the
substring as well or the string pause
rather sorry so echo STR pause this is
this which is changing room remember and
we'll put a break on the end of that so
we're going to be output the string
position then the offset then the string
position again then the offset because
we've got two instances of cat so search
for cat replace with monkey finding
replace so let's type this again cat so
at position 4 1 2 3 4 we find the word
cat we skip this because we know the
positions are that's fine we can do we
can replace that later with the
substring replace function 1 2 3 on is
at position 7 so 4 5 6 7 now we begin
searching from here so 1 7 8 9 10 11 12
13 14 15 16 17 18 19 at 19 here we find
the instance of the word cat and 3 later
we end up with 22 now at this point
we're at the end of the string so in our
program this is going to evaluate to
false so we're going to break the loop
it's as simple as that thinking about it
however when you are writing it you
might find it a bit hard to get around
the logic so if I was to say cat cat cat
after this and I'm searching for cat
again monkey doesn't matter right now
and I can replace we get a whole bunch
of variables AB numbers here sorry
telling us the position and where we're
starting from after the same if I was to
just type monkey search for monkey and
replace with cat for example finding
replace o monkey monkey
oh okay okay we'll address this issue
later and when we test it